The invention relates to a hot-gas reciprocating engine comprising a heater serving as a heat exchanger which is situated inside a heat pipe and includes a bundle of heater pipes which communicate on the one side with a working space of variable volume and higher temperature during operation inside a cylinder unit, and communicate communicating on the other side with a regenerator unit. The heater pipes on at least one side of the bundle of pipes are connected to the relevant unit by way of one or more tubular connection members which are passed through a wall of the heat pipe.
Hot-gas reciprocating engines of the kind set forth are known as appears from the FIGS. 13 and 16 of the article "Prospects of the Stirling engine for vehicular propulsion" (Philips Technical Review, Vol. 31, 1970, No. 5/63,402,767.
Eaxmples of heaters of hot-gas reciprocating engines which are composed of bundles of pipes are described in British Patent Nos. 708,199 and 898,270, while for the properties of heat pipes reference is made to, U.S. Pat. Nos. 3,229,759 and 3,402,707.
The tubular connection members which connect the heater pipes to the cylinder unit and the regenerator unit, respectively, in the known hot-gas reciprocating engines are passed through the rigid bottom plate of the heat pipe and extend parallel to the center line of the relevant unit.
A problem of this construction are the large material stresses occurring in the bottom plate and the connection members during operation of the engine, thus causing leakage of the heat pipe and of the heater pipes through which the working medium of the engine (for example, helium or hydrogen) flows. Because of the thermal expansion occurring at the relevant operating temperatures of approximately 800.degree. C, the diameter of the bottom plate is substantially increased. In addition, the parts of the cylinder and the regenerator which are at a high temperature also expand, while the parts of the cylinder and the regenerator which are at a low temperature are rigidly connected to each other, thus causing relative displacement and rotation of the parts of higher temperature. The said material stresses thus appear.
It could be contemplated to make the construction of the bottom plate of the heat pipe flexible. However, on the one hand it is very difficult and expensive to manufacture such flexible plates, and on the other hand this would necessitate the use of thin plates. The latter is not acceptable because, depending on the operating temperature, the pressure of the heat transport medium in the heat pipe (for example, sodium or lithium) is usually lower or higher than the ambient atmospheric pressure. The pressure difference on both sides of the plate then causes pressure forces or tensile forces to be exerted on this plate. The thin plate at a high temperature has insufficient mechanical strength to withstand these forces in the course of time.
The invention has for its object to provide a hot-gas reciprocating engine of the kind set forth in which the said problems are eliminated.